Initiator tRNAMet genes from the nematode Caenorhabditis elegans

Five different members of the initiator tRNAMet gene family have been isolated and characterized from the nematode Caenorhabditis elegans. All five show identical tRNA coding sequences, followed by a block of T residues associated with termination by RNA polymerase III. Nucleotide sequences flanking the tDNAs are completely divergent, except for two distinct members with identical flanking sequences, which may have arisen from a recent gene duplication event. Each tDNA is also flanked by middle-repetitive DNA, but the lack of cross-hybridization to each other suggests that these repetitive sequences have no common functional significance. The tRNAMeti genes do not appear to be closely linked to each other, although in vitro transcription reveals a putative tDNA adjacent to one member. Finally, there are large differences in the extent to which the five genes are transcribed by a homologous C. elegans cell-free extract, suggesting that flanking sequences have a significant effect on transcription by RNA polymerase III.